The present invention relates to a computer system suitable for, for example, easy-to-carry information equipment for personal use, and more particularly to a computer system capable of reducing the unnecessarily consumed electric power remarkably.
One known method of controlling electric power in microprocessors mounted on conventional information equipment is to reduce the power consumption by decreasing the frequency of the clock or stopping the clock when the system is idling.
Another known method of decreasing the power consumption in the entire system is to reduce the power consumption by stopping the supply of power to the input/output devices that are presently out of use.
In the techniques realizing these methods, since the component parts to which the supply of power may be stopped are limited, the unnecessarily consumed power cannot be reduced sufficiently. For example, portable information equipment operating from the power supplied from a battery pack containing a secondary battery has encountered the problem of having to shorten the possible operating time of the system.
FIG. 1 shows the configuration of a conventional computer system. In the computer system, a power supply section 34 supplies electric power under the control of a power sequence controller 33. In response to the control signal transmitted from a processor 10 via an IO bus 3a, an IO bus bridge 32, and an IO bus 3b, the power sequence controller 33 controls the power supply section 34.
In such a conventional computer system, for example, even when all the devices, including device 31a and device 31b, connected to the IO bus 3a have been out of operation for a long time, a command signal to stop the supply of power to the IO bus 3a is not transmitted to the power sequence controller 33.
As described above, the conventional computer system has the following problem: the unnecessarily consumed power cannot be reduced sufficiently and therefore the possible operating time of the system has to be shortened in portable information equipment operating from the power supplied from, for example, a battery pack containing a secondary battery.